Rotary furnace



N0V- 8, l938- G. F. BLASIER ROTARY FURNACE Filed Dec. 17, 1937 2 Sheets-Sheet l INVENTOR Geo/"ge 'zifer ATTORNEY v Nov. 8, 1938. G. F. BLASIER ROTARY FURNACE 2 .Sheets-Sheet 2 Filedv Dec. 17, 19:57

lll/lll lNvENToR eafye 'laszef ATTORNEY Patented Nov. 8, 1938 UNITED sTATEs ROTARY FUBNACE George F. Blasier, North Tonawanda, N. Y., assigner to Builalo Bolt Company, North Tonawanda, N. Y., a corporation of New York Application December 17, 1937, Serial No. 180,300

28 Claims.

This invention relates more particularly to furnaces of the rotary tubular type, wherein rotation of the furnace is utilized for introducing. advancing and discharging articles or materials while progressively heating them by flame discharging into the furnace through the exit end thereof.

'I'he present illustrative form was primarily designed and is herein shown as embodied in a furnace for annealing and heat treatment of metal articles such as steel nuts, bolts, or the like, but it will be obvious that various novel features of construction and operation of my furnace will be found useful in other rotary tube furnaces,

u and for heat treatment of other articles or materials, for other purposes.

As shown herein, the outer tubular shell, and the rotating, intake, exit, and name-projecting arrangements, may be in a general way, similar to those shown in the U. S. patent to Rockwell, No. 1,333,343; but the present invention relates more particularly to a novel inner shell construction in place of the inner lining; novel means for supporting said inner shell in said outer tubular shell independently of the intermediate insulation; a novel construction for the means whereby rotation of said shell propels the articles or materials from the intake to the exit end of the furnace and also novel combinations of the various novel features with each other, and with said outer shell, and with its rotating, intake, exit, and name-projecting arrangements.

In furnaces of the above type, the cylinder may be, say, feet long, by three feet or more internal diameter, and the interior is provided with a helical flange or rib. When the cylinder is rotated, the articles are carried by the cylindrical and helical inner surfaces, up to where gravity causes them to successively and progressively fall o downward so that the helical rib surfaces operate to propel the articles toward the exit end of the furnace.

For annealing and heat treatment of metal articles, the inner lining and the helical flange is subjected to rather high temperatures, and to correspondingly high variations of temperature. For instance, in a given case, the temperature adjacent the exit end of the cylinder may be something like 1500 F., while the temperature at the .50 entrance end may be only 300 or 400 F. It

results that both radial and longitudinal expansion and shrinkage of the inner lining varies greatly between the exit and the entrance; and in the aggregate, the total amount of longitudi- 55 nal expansion and shrinkage is very substantial.

For these reasons, it has been common to make the inner lining and its ribs of cast iron. But cast iron is brittle and the castings are heavy,

so the prior practice has been to build up the inner lining from cylindrical castings each hav- 5 lng a section of the helical rib integral therewith. These cylindrical sections may be 15 .inches to 18 inches wide. lengthwise of the furnace, so that it may take 8 or 10 of them to complete an inner lining. They are supported by an interme- 10 diate lining consisting of arch brick resting on the exterior cylinder and presenting inner circular surfaces which support the cylindrical castings. In practice, the arch brick interlining with the successive cast iron sections thereon, is built l5 up progressively from one end of the furnace to the other.

There are many objections to such constructions. One obvious objection is that the weight of the separate inner castings, the continuous 20 rotation of the furnace, and the repeated expansion and contraction of the cast iron due to lighting up and turning oil the heat, cause the castings to pound themselves loose in the brick, and in time this necessitates re-bricking and re-lining the entire furnace; and, in many 'cases the inner cast iron sections are so badly distorted by the heat that they cannot be re-used.

In this connection, it is to be noted that both the arch brick and the cast iron cylinder sections afford substantially no resistance to longitudinal tension, and they can contribute to transverse stiness of the rotating furnace as compression members only; and their effectiveness even for this purpose depends on careful fit against one another and against the exterior shell. But the cast iron inner lining and the arch brick have substantially different coeilicients of expansion; also the amount of the expansion and contraction of the inner cast iron, is different from that of the outer iron shell, because of the great difference in temperature between the interior which is directly heated and the exterior which is relatively cool because it is protected by intervening 5 insulation, and is cooled by the outer air.

The present invention obviates these objectionable features by introducing an entirely new principle of construction.

In place of the many relatively short cast iron 5 sections, I substitute a single integral tubular shell running the entire length of the furnace. Preferably, this is made from rolled, heatresisting steel sheet or plate material, of thickness and construction such that said inner tube shell may have nearly or quite as great strength as the outer shell.

'I'his inner tube shell is anchored to the exterior shell at one place only, preferably at the exit opening where the finished articles fall out of the furnace. 'Ihis would not be possible with the old type construction described above. because any radial expansion of the sectional cast rings would cause them to lodge or bind tightly against the insulating brick, thereby preventing free expansion longitudinally of the furnace.

My inner tube shell is mounted in the outer shell by bearing -surfaces which permit it to be inserted and removed endwise, as a unit, and which permit it, when heated, to expand longitudinally by sliding in both directions from the above described anchorage point.

The supports permitting such endwise sliding, are rings fastened to the outer shell, and they have bearing members extending inward a distance equal to the thickness desired for the heat insulation; and the insulation itself is suitable refractory aggregate which can be inserted in or removed from the interspace without disturbing either the outer shell or the inner shell.

Another feature is making the inner propelling members in the form of short lengths of helically disposed bar material, each length being secured to the inside of the inner shell, by riveting, or by welding, or preferably by both; and preferably at certain spaced-apart points, so that the expansion and contraction of these members may be somewhat different from that of the inner shell, without thereby distorting either themselves, or said shell.

The above and other features of my invention may be more fully understood from the following description in connection with the accompanying drawings, in which Fig. 1 is a longitudinal sectional view in a vertical plane including the axis of the furnace and corresponding to the line I-l, Fig. 3;

Fig. la is a similar section of a characteristic short length of the cylinder, but on a large scale so as to facilitate illustrations of some details;

Fig. 2 is a diagram showing the inner cylindrical surface of the furnace, the entire circumference of the cylinder being unrolled to the vertical plane of an up-turning straight line element, so as to give a diagrammatic indication of the disposition and operation of the successively upturning helical flights, with respect to gravity;

Fig. 3 is an end view of the furnace, from the left, Fig. 1;

Fig. 4 is a transverse section on the line 4-4, Fig. 1, the granular insulating material being omitted;

Fig. 5 is a detailed perspective showing the laterally corrugated rings whereby the inner shell of the furnace is supported slidably but keyed against the rotation;

Fig. 6 is a detailed view of the innershell and one of the key strips shown in Fig. 4, but on a much larger scale;

Fig. '7 is a detailed view showing a portion of the inner cylinder and key strip, in perspective as well as in section.

Referring first to conventional features of one form. of furnace to which my new principles of construction have been applied:

(a) The outer shell I is conventionally indicated as provided with riding rings 2, 2, and rolls 2a, 2a, whereby it is supported for rotation in the desired direction and at desired rates, by any suitable mechanism, not shown, but which preferably includes a variable speed electric motor.

(b) The articles are charged into the furnace through opening 3, and, as the furnace rotates, they slide to the larger diameterend of chamber 3a and are then picked up by the edge 3b of a slanting, more or less spiral scoop 3c, which extends to the peripheral wall of said chamber la. As the furnace rotates farther, gravity causes the articles to slide inward on the scoop, and ultimately to fall into the furnace through the opening 3d.

(c) A stationary hood 4 at the exit end of the furnace, surrounds the annular path of travel of the open outlet through which the heated articles fall out of the furnace. This hood is designed to limit escape of flame and hot gases from said outlet, particularly during the upper half of its rotation, when it is upwardly directed, and would otherwise tend to act as a chimney discharging directly into the open air. The upper annulus 4 connects with a stationary chute 4a, into which the hot nuts or other articles fall when the outlet is downwardly directed as in Fig. 1. This chute 4a serves as a connection between furnace and quench tank which may contain water or oil or other fluid for chilling or otherwise modifying the quality of the heated articles; or, in case of annealing, it may contain only air, for air-cooling.

(d) The burner 5, whereby flame is projected axially into the furnace, may be of any known or desired construction, as also the cooperating insulation through which the flame is discharged, although some features of the latter are new, particularly as concerns the novel wayin which the insulation is supported by the furnace.

For my purposes, the outer shell l, is preferably made of rolled plate of thickness and strength sufilcient to carry the load of the entire rotating structure, say, It, inch thick; and the cylinder may be built up from the plate material in any of the ordinary ways, as by riveting and welding, but 'for my purposes the inwardly presented ends of the rivets are preferably ush with the interior surface of the shell.

The inner shell may be made from rolled steel sheets or plates, of considerable thickness and of heat-resisting qualities adequate for sustaining the structural strains and the maximum temperatures above indicated. For such reasons, the inner shell is preferably thicker than the outer shell, say, inch instead of 1l; inch.

An important feature of this inner shell is making it externally smooth and uniform enough so that it will be endwise slidable when it lengthens by heating or shortens by cooling; preferably also for easy endwise insertion into and removal from the outer shell. For these and other reasons, a novel construction .in accordance with my present invention is highly desirable. In my construction, the inner shell is made from a plurality of rolled metal plates extending the full length of the furnace. These long plates or strips are transversely curved on the arc of a circle of the diameter desired for the inner shell. As shown in Fig. 4 and also on a larger scale in Figs. 6 and '7, there are preferably only two such strips 6a, 6a, each transversely curved to form a semi-cylinder. These semi-cylinders are assembled in a practically integral cylinder without any joints or projections except at the meeting edges of the semi-cylinders. A very effective way of making this joint, is to place the edges of the sheets in registering contact,

before inserting them in the outer shell. Then a long plate or strip lb. which may be, say, 3 inches wide, is secured over the contacting edges of the sections by rivets tc. Then the two corners where the edges of the strip contact the outer surface of the shell, are welded throughout the length of the shell, as indicated at 6d.

for the inner shell; but

A long rectangular bar le, is next placed edgewise along the center of this strip, and welded to it throughoutdts entire length as indicated at if. These bars ld, 6e are utilized as a spline whereby the inner shell is endwise slidable, but is keyed against rotation.

As shown in Fig. l, this inner shell is slidably supported in the outer shell. by end bearings, and by suitably spaced intermediate bearings 1, 1; which latter are preferably castings of metal capable of withstanding high temperature, preferably a nickel-chrome alloy such as Misco. As shown in Fig. 5, each bearing 1 is an annulus of lrelatively thin metal reversely curved in transverse accordion-like fiutings 1a, of which the outer and inner edges, 1d, 1e, constitute cylindrically disposed bearing surfaces. The depth of the flutings determines the effective width of the bearing `surface lengthwise of the furnace. In aparticular case, the ilutings were '1 inches high radially; 3 inches lengthwise of the furnace; and the metal was inch thick.

Edgewise, the' thin metal is substantially radial, so that the annulus affords rigid support the transverse flutings so that heat expansion or distortion takes effect only as slight circumferential compression of said fiutings, without anydistorting or binding effect on the shells. To permit such functioning, the annulus is anchored to the bute'r sneu only-at intervals', with one, or preferably several, intervening iiutings unanchored; and, for similar reasons, the anchorages are preferably on adjacent convex bends on the same face lof the casting, as indicated in Fig. l and Fig. 5, where angle fittings, 1b, are shown as welded to the flutings and bolted to the outer shell. l

As shown in Figs. 5 and 6, opposite flutings are cut away to form keyways 'Ic for the flat strips Gb and the key bars 5e. As shown, there is substantial clearance space between the keys and keyways, as also between the inner shell l and the bearingrings 1. "Experience shows that with the construction described above, an all around clearance of about of an inch when the parts are coldj/is sufficient. In practice, this does not involve any undue looseness. it being only sufficient to allow a' good endwise sliding nt when the furnace is hot.

There are also, slidable bearings between inner and outer shells at each end of the furnace. As shown in Fig. 1, the exit end of the inner shell 6 extends beyond the end of the outer shell i, and, as shown in Fig. 3, this end of the outer shell is closed in by an annulus which is made in two semi-circular sections, la and l b,`secured together by bolts, and, as indicated in Fig. 1, rigidly bolted to an angular annulus which is welded to the outer shell i. The end closure has a broad cylindrical extension ic which, through an intermediate thin packing id, affords a slidable bearing for this end of the inrer shell.

At the other end, the inner surface of the inner shell 6 has slidable engagement with the outside surface of a projecting annulus le. which is preferably'cast on an end closure ld, which areA springy, of the annulus is rigidly secured between ends of outer shell i, and supply chamber la..

The six slidable bearings described above have incidental advantages in connection with the construction and assembly of the parts of the furnace. When the end closures la, ib, are removed, or before they are put in place, the inner shell 8 formed as above described, and provided with an outlet casting, Sz, welded thereto, easily slides endwise through the ring bearings, until its free end slides over the outer surface of said inwardly projecting annulus ie.

The anchorage of the inner shell to the outer shell is then effected by means of a somewhat larger outlet casting im, which surrounds the outlet casting 6x and is bolted to the outer shell i. The thin clearance space between these castings is' then filled solid with refractory packing. Thus, the inner shell is securely anchored to the outer shell as concerns longitudinal movement; and as above described, the inner shell is free to expand longitudinally, in both directions from this anchorage, toward the firing end, and also toward the intake end. Thereafter the semicircular closure sections la, Ib, are bolted toone another and to the outer shell, thereby closing the interspace between shells and affording a wide bearing surface on which this end of the inner shell may slide.

The projecting end of the inner shell 8, carries the internally coned insulation 5a for spreading the flame, and this is preferably built in after said shell 8 has been put in place. Thereafter the'smaller name directing insulating members 5b, 5c, are arranged in the end closure Ih of inner shell 6, and said closure is then secured to the end of said inner shell 6. The fuel prolector l can be then placed in position.

After the inner shell 6 is in position, "the interspaces between the ring bearings 1, are filled with refractory insulating material. As indicated at 8, I, Figs. 1 and 2, this is preferably loose aggregate or lump material, preferably free from fine particles. This material may be broken fire brick, but I prefera burnt slate product known as Haytite". A satisfactory range of the sizes for the lumps, includes such as will pass a one-inch screen and such as will not pass a half-inch screen. Such sizes are too large to pass through the clearance spaces between the inner shell and the bearing surfaces; but in time tumbling of the loose aggregate during rotation, will wear off or break off some nner pieces, and these will tend to sift out through all bearing surfaces; and my construction is designed to obviate objectionable effects which would result.

Sifting out at the exit end of the furnace is made difllcult, by having the broad close fitting bearing surface at Ic, ld, but, as a further precaution, I provide a clamping ring 5g; and, after the furnace has been heated up and normal maximum expansion of the inner shell l has been effected, this ring is set tight against the end of bearing Ic, and is rigidly-clamped in place. When the furnace cools, causing endwise shrinkage toward the interior of the furnace, it also causes radial shrinkage, thereby relieving the tightness of the ring.

At the other end, where the inner shell has maximum longitudinal movement when contracted and expanded by heat, some difficulty is encountered, but this is taken care of by packing this interspace with steel turnings 8a. which catch and hold any particles of aggregate that might otherwise escape in this direction. Pref erably the steel turnings are prevented from reaching the place where the free end of inner shell 6 slides on annulus le, by an annular partition If, which is rigidly secured to the outer shell I, but is not secured to inner shell 8.

Sitting from one compartment to another, through the ring bearings 1, is not objectionable because the bearing surfaces afforded by the inner edges of the corrugations are too narrow to permit any accumulationof the abraded insulating material, such as would prevent free endwise sliding of the shell.

Manholes of suitable size and location for packing the aggregate and steel turnings into the lnterspaces between the inner and outer shells are assumed; and are more or less diagrammatically indicated on Fig. 1 as having cover plates Ig, which are thick enough and are secured by bolts and nuts strong enough so that structural strength of the outer shell l, is not impaired by the manholes.

While a furnace such as above described might be mounted on an inclined axis -so that progress of the articles or materials from entrance to exit would be partly or even wholly, by rotary tumbling, the primary purpose of the whole design, is to successfully apply interior ribs or segments adapted to uniformly feed, tumble and heat a continuous stream of the articles or materials, when the axis is horizontal, or approximately so.

In the prior art, the ribs used for propelling the articles through the furnace, particularly those near the hot exit end of the furnace, are so high that their innermost edges are close to the axial flame whereby the furnace is heated, and said ribs necessarily get much hotter than the cylinder part of the casting. Consequently, repeated heating and cooling brought about great distortion of the entire casting, so much so that the casting would break loose from the brick, and'wreck the interior. Even before this happened, the helical rib segments would become misaligned, thereby affording lodging places where some of the articles would be held and mined by overheating. These primary conditions are what brought about my idea of making the inner lining continuous.

At first, ll assumed that for my continuous inner lining I would have to have fairly high ribs, as in the prior art, and I tried a continuous helix made up in sections and secured to the inner lining by riveting and welding. These sections consisted of helical castings, L-shaped in cross-section, but with rib height only about two inches.

However, I found in practice that even with this greatly reduced cross-section, unequal contraction and expansion by repeated heating and cooling, operated to greatly distort the continuous inner shell.

My next thought was to make the helix from rectangular sections of very much less height, approximately 1 inch high and 11/2 inches wide. This would ailord only 1 inch of forward wedging surface forpropelling a stream of articles that may be two inches or more in depth. In such case the tendency would be for the helix to act positively on only the lower layers of the stream. The feed would be thus much less positive and would allow much more slip than the high ribs of the prior art. Such a continuous helix can be built up from such sections and with a plurality of such helices, analogous to a 2-thread or 3-thread screw, the forwardly wedging surface area may be multiplied so as to give a practically useful rate of feed, but I have discovered that even when built from these rectangular sections only 1 inch high by 11/2 inches wide, a continuous helix of conventional pitch, is likely to cause distortion of the inner shell.

Ultimately I discovered that it is not necessary to have the helix sections continuous; that I can provide propelling surface adapted to ensure a constant uniform flow of the material through the furnace, by widely interrupting and uniformly distributing the sections, in flight formation; and that many advantages result. 'I'he total forward wedging area may be multiplied as much as may be desired; the`forward wedglng angle of the flights may be selected, independently of any helical relation betwen them; the flights being-low as compared with the depth of the stream of articles, the mixing of the articles ln the stream will be thorough and will be uniform throughoutl the length of the furnace; and the heating will be correspondingly uniform.

structurally considered, the pitch of the flights may be about the same as that common for the single helix of the prior art, so that they contribute longitudinal, as well as circumferential reenforcement for the inner lining. Apparently also diagonal stresses due to contraction and expansion of the distributed diagonal flights have much less tendency to cause distortion of said inner lining, than would a single helix of the same total length. This is particularly true when the flights are secured in accordance with my present invention, by riveting and welding at selected points, widely spaced apart longitudinally of the flight. There is of course latitude for considerable variations in the forward wedging angle of the flights, the number of flights, and their distribution, but the arrangement shown herein has proved highly successful in practice as concerns uniformly feeding a relatively deep stream of the articles through the furnace; and uniformly mixing the stream so that all articles are heated uniformly. This applies as to a wide variety of products to be heated, my furnace having been successfully used where the stream consists of small articles, such as nuts for quarter inch bolts, as well as large articles, such as bolts 61/2 inches long by 1 1/8 inches in diameter; the flights being an inch high and the thickest part of the stream about 2 inches deep. As shown in Fig. la, the flights were secured by Widely spaced rivets 9x, supplemented by welding the flight to the inner shell, adjacent the rivets only, as diagrammatically indicated at Sy. There are, of course, many geometrical patterns whereby the desired length of flight, affording the desired total forward wedging area, may be attained. On superficial consideration, Fig. l might seem to indicate three helical threads, each interrupted by Wide spaces between the ends of successive flights. Such an arrangement would be practical, but as a matter of fact, uniform distribution of the flights, as well as flexibility as concerns designing the length and feed pitch of the fli/ghts, was actually attained by following a somewhat different geometrical theory. This is best seen by reference to the diagram Fig. 2, which shows the geometrical relation of the flights, with respect to the direction of gravity and rotation, the internal surface of the shell being unrolled to a flat, vertical plane, and the flights being identified by the same numbers as used in Fig. l.

This diagram covers the exit end and a characteristic adjacent length of the inner shell. This is partly for the purpose of showing the cooperative relation of the nights at the exit end, with respect to the outlet opening x. Y

The arrangement of the nights follows a `hypothetical helical thread indicated by the dotted line b-c, and other lines parallel therewith. This hypothetical thread would have a feed pitch oi about 9; but instead of having continuous rib sections along this helical line, the sections have been pitched 16 rearward of the hypohetical helix line b-c. Thus the actual feed pitch of each night with respect to the gravity line a-b, is about 25. This approaches, but is slightly less than the feed angles used for the continuous helix ahown in the above specined Rockwell patent.

Preferably, the upper end of each night aligns horizontally with the lower end of the night next above it, as for instance, any night 9 with respect to the next night la; llt-9b; etc.

The night length is such that there are 35/2 nights, I, 9a, lb and half of 9c, for each 360 turn of the hypothetical helix. l (See also Fig. 4.) The point about this is that having an odd half night per 360 turn, brings the middle of every night in horizontal alignment with the ends of adjacent nights in frontof, and behind it.

In the direction of gravity, the discharge end of each night aligns vertically with the center of the next night below it. When the nights'are on the upturning side. as shown in Fig. 2, this puts successive nights in a sort of cascade relation with respect to the down tumbling nuts. Thus, a nut tumbling over the edge of the lower half of one night, is likely to be intercepted by the forward feed surface of the next lower night. `Furthermore, when the nights are on the down turning aide, near the bottom (see Fig. 1) the leading ends of successive nights, cut into the stream of nuts at a point back of where they would be if each night had been high enough to positively screw propel all nuts in its path, instead of allowing those in the top layer to tumble over its top edge.

Considering the nights further with respect to the hypothetical helix lines b-c, along which they are arranged, it will be seen that, because of the odd half night per turn, all relations of the nights can be shown only by considering 'l nights that make two turns of said helix; and that is why the nights are separately identified on the drawings as 9, 9a, 9b. 9c, 9d, 9e, 9j; and it is only after 9j that the arrangement repeats, beginning again with another night 9.

Inspection of Fig. 1 will show that in this special case, there are six of these complete series of nights beginning with a night 9, and as each series has seven nights, there are approximately 42 nights. In this case, the night-equipped length of the inner shell, was about 13 feet, and its inner surface was about 7 feet 2 inches in circumference; and for these dimensions, each night was made approximately 261/2 inches long; so the total night length ngures out about 93 feet for this 13 feet length of inner shell.

If the same 25 nights were arranged as a continuous 25 helix, the total night length would be only 45 feet, or less. Thus two such continuous helices, arranged like a two-thread screw, would afford less night length than is afforded by the present interrupted night relation. Obviously, any such twohread screw arrangement, could be improved by two features of my present invention. One would be arranging them so that joints between sections in one helix are in horizontal alignment with the center of adjacent sections in the other thread, thereby contributing toward more uniform structural stiffness of the inner shell I. Another would be spacing apart the ends ofall sections far enough so that nuts or bolts could not lodge between them.

Even where widely separated, uniformly' distributed nights are used in accordance with all the basic principles of my present invention, it will be obvious that either the pitch of the hypothetical helix or'the feed pitch of the nights, or both, may be varied. Preferably, increase of feed pitch of the nights would be accompanied by increase in pitch of the hypothetical helix and vice versa.V Moreover, it is not necessary that either the hypothetical helix, or the feed pitch of the nights, be the same throughout the entire length of the inner shell; and though desirable, it is not essential to have the length or spacings of the nights the same. Variations may be desirable for the purpose of expediting distribution and streaming out, of the articles dumped in at the supply end of the furnace, or to slow down the feed through the middle zone of the furnace, or to accelerate discharge through the hot end.

yCertain details of the individual nights have speclnc advantages, regardless of how they are distributed. Having it rectangular in cross-section ensures a front propelling face perpendicular to the inner surface of the shell, so that there is less tendency for the stream of articles to slip over the top surface of the night. Having the cross-section uniform as well as rectangular throughout the length of the night, decreases -tendency to unequal expansion and distortion when heated. Having it of less height than the deepest part of the stream of articles propelled thereby tends to keep the temperature lower and more uniform. Having it of greater width than height gives more uniform temperature between the hot top surface of the night and the portion of the inner lining in contact with the bottom surface thereof. Every fraction of an inch decrease in height of a night gives more than proportional decrease in the straightening and distorting enects which normally result from any given difference in temperature between a top surface of a night and a radially remote bottom surface. Having short nights, limits the amount of distortion that can be applied at any one place on the inner shell, by end to end lengthening, straightening or distortion of the night.

Any and all of the above advantages may be cheaply and easily attained by forming the nights from rolled rectangular bars, cut to proper vlength and bent to yshape suitable for riveting and welding to the inner shell at a plurality of suitably spaced points, as above described. These bars may be of any sufficiently heat resisting metal, but I prefer a nickel-chrome alloy such as Misco.

I claim:

1. A tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a name jet in the opposite direction; said furnace including an outer shell; spaced-apart, inwardly-extending annular bearings carried by said outer shell; a cylindrical, single-piece inner shell constructed of heatresisting plate or heavy sheet metal, fitting and longitudinally splined to said bearings; and refractory heat-insulating aggregate packed in the interspaoes between said shells and said bearings; said inner shell extending beyond the outer shell at the exit end of the furnace and having therein'an annulus of refractory heat insulating material formed with internal diverging surfaces serving as an expansion nozzle for a flame jet projected therethrough.

2. A tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a llame jet in the opposite direction; said furnace including an outer shell; spaced-apart, inwardly-extending annular bearings carried by said outer` shell; a cylindrical, single-piece inner shell constructed of heat-resisting plate or heavy sheet metal, fitting and longitudinally splined to said bearings; and refractory heat-insulating aggregate packed in the interspaces between said shells and said bearings.

3. A tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough; and means for projecting a flame jet in the opposite direction; said furnace including an outer shell; spaced-apart, inwardly-extending annular bearings carried by said outer shell; and a cylindrical, single-piece inner shell constructed of heatresisting plate or heavy sheet metal, fitting and longitudinally splined to said bearings.

4. A tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer shell; spaced-apart, inwardly-extending annular bearings carried by said outer shell; and a cylindrical, single-piece inner shell constructed of heat-resisting plate or heavy sheet metal, fitting and longitudinally splined to said bearings; said inner shell extending beyond the outer shell at the exit end of the furnace and having therein an annulus of refractory heat insulating material formed with internal diverging surfaces serving as an expansion nozzle for a flame jet projected therethrough.

5. A tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer shell; a single-piece inner shell longitudinally slidable in said outer shell to permit lengthening when heated, and anchored to it only in a short zone intermediate its ends, so that said inner shell is free to slide in both directions from said anchorage when longitudinally expanded or contracted by heating or cooling of the furnace.

6. A tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer tubular shell of rolled steel capable of supporting the entire load of the furnace; spaced-apart, inwardly-extending annular bearings carried by said outer shell; a single-piece inner shell of rolled plate or heavy sheet, heat-resisting steel, longitudinally slidable to permit it to lengthen when heated; and means for anchoring only a short portion of its length to said outer shell.

7. A tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer tubular shell of rolled steel capable of supporting the entire load of the furnace; a single-piece inner shell of rolled plate or heavy sheet, heat-resisting steel, longitudinally slidable to permit it to lengthen when heated; and means for anchoring a short portion of its length to said outer shell, to limit endwise sliding except by endwise lengthening.

8. A substantially horizontal tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer tubular shell capable of supporting the entire load of the furnace and having inwardly extending annular bearings having keyways formed therein, and a single-piece inner shell having walls of rolled plate or heavy sheet, heat-resisting steel; with external rigidly-secured longitudinal ribs adapted to engage said keyways, and internal rigidly-secured, inwardly-A projecting, diagonally-disposed, forwardly feeding ribs of heat-resisting metal.

9. A substantially horizontal tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer tubular shell capable of supporting the entire load of the furnace and supporting. coaxially therewith, a single-piece inner shell having walls of rolled plate or heavy sheet, heatresisting steel, having external rigidly-secured longitudinal ribs whereby the inner shell is keyed for rotation with the outer shell, and internal rigidly-secured, inwardly-projecting, diagonallydisposed, forwardly-feeding ribs of heat-resisting metal, said latter ribs being short sections of rolled bar, bent to nt the interior surface of said shell and secured thereto by riveting and welding.

10. A substantially horizontal tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer tubular shell capable of supporting the entire load of the furnace and supporting, coaxially therewith, a single-piece inner shell having walls of rolled plate or heavy sheet, heatresisting steel, having external rigidly secured longitudinal ribs whereby the inner shell is keyed for rotation with the outer shell, and internal rigidly-secured, inwardly-projecting, diagonallydisposed, forwardly-feeding, ribs of heat-resisting metal, said latter ribs being short sections of rolled bar, bent to fit the interior surface of said shell and secured thereto by riveting and Welding relatively small-area, spaced-apart portions of each rib section.

11. A substantially horizontal tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer tubular shell capable of supporting the entire load of the furnace and supporting, coaxially therewith, a single-piece inner shell having walls of rolled plate or heavy sheet, heatresisting steel, and having inwardly-projecting, helically-disposed, forwardly-feeding, spaced apart flights of heat-resisting metal, said flights being relatively short sections of rolled bar, bent to fit the interior surface of said shell and secured thereto by riveting and welding relatively small area spaced apart portions of each ight.

12. A substantially horizontal tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a llame jet in the opposite direction; said furnace includ- 14. A furnace as specified in ing an outer tubular shell capable of supporting the entire load of the furnace and supporting, coaxially therewith, a single-piece inner shell 'having walls of rolled plate or heavy sheet, heatresisting steel, and havinginwardly-projecting, helically disposed, forwardly-feeding flights of heat-resisting metal, riveted to the inner surface thereof.

13. A substantially horizontal tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer tubular shell capable of supporting the entire load of the furnace and supporting,

coaxially therewith, a single-piece inner shell having walls of rolled plate or heavy sheet, heatresisting steel, and having inwardly-projecting,

helically disposed, forwardly-feeding flights of heat-resisting metal, rigidly secured to the inner surface thereof, said fiights being of short length as compared with a semi-circumference of said inner surface.

claim 13 and in which the flights are of substantially uniform, substantially rectangular cross-section.

15. A furnace as specified in claim 13 and in which the flights are of substantially uniform rectangular cross-section and are of greater width than thickness.

16. A furnace as specified in claim 13 and in which the flights are distributed with substantial uniformity and are arranged in generally helical relation but spaced-apart endwise.

17. A substantially horizontal tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a ame jet in the opposite direction; said furnace including an outer tubular shell of steel capable of supporting the entire load of the furnace; an inner cylinder formed from heat-resisting metal; and means for supporting said cylinder coaxially in said outer shell; said inner cylinder having integrally united with the inner surface thereof, inwardly-projecting, helically-disposed, forwardly-feeding flights made of heat-resisting metal, said flights being of short length as compared with a semi-circumference of said inner surface, and spaced-apart endwise, distances which are great as compared with the sizes of the articles to be propelled thereby.

18. A furnace as specified in claim 17 and in which the flights are distributed substantially uniformly and in overlapping relation circumferentially, with respect to gravity.

19. A furnace as specified in claim 17 and in which the flights are distributed substantially uniformly and in overlapping relation in the direction of lengthwise feed in the furnace.

20. A furnace as specified in claim 17, and in which the fiights are of small height as compared with the depth of the stream of articles or materials advanced thereby.

21. A furnace as specified in claim 17 and in which the flights are of less height than the depth of the stream of articles or materials advanced thereby, and are distributed along a helical line which is of low pitch as compared with the feed pitch of the individual ights.

22. A furnace as specified in claim 17, and in which the flights are of less height than the depth of the stream of articles or materials advanced thereby, and are uniformly distributed along a helical line the pitch of which is less than half the feed pitch of the individual flights.

23. A tubular furnace, means for peripherally A supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer shell; spaced-apart, inwardly-extending bearings carried by said outer shell; a single-piece inner shell fitting said bearings; and refractory heat insulating aggregrate packed in the interspaces between said shells and said bearings; said bearings including a cylindrical bearing fitting the exterior of the inner shell, carried by an annular closure for the space between the inner and outer shells at the exit end of the furnace; an external bearing fitting the interior of said inner shell, carried `by an end closure for said interspace at the entrance end of the furnace; and intermediate spaced-apart bearings, each consisting of an annulus'formed as a thin metal wall substantially perpendicular to the axis of the furnace, and transversely curved in accordion-like fiutings affording substantial circumferential elasticity; and means securing the flutings to the outer shell only at spaced-apart intervals permitting circumferential elastic compression of the annulus when expanded by heat.

24. A tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer shell; spaced-apart, inwardly-extending bearings carried by said outer shell; and a single-piece inner shell fitting said bearings; said bearings including a cylindrical bearing fitting the exterior of the inner shell, carried by an annular closure for the space between the inner and outer shells at the exit end of the furnace; and an external bearing fitting the interior of said inner shell, carried by an end closure for said interspace at the entrance end of the furnace.

25. A tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a ame jet in the opposite direction; said furnace including an outer shell; spaced-apart, inwardly-extending bearings carried by said outer shell; and a single-piece inner shell fitting said bearings; said bearings including spaced-apart bearings intermediate the ends of the shells, each consisting of an annulus formed as a thin metal wall substantially perpendicular to the axis of the furnace, and transversely curved in accordion-like fiutings affording substantial circumferential elasticity; and means securing the fiutings to the outer shell only at spaced-apart intervals permitting circumferential elastic compression of the annulus when expanded by heat.

26. A furnace as specified in claim 25, and in which each annulus is a casting of heat-resisting metal.

27. A furnace as specified in claim 25, and in which each annulus is a casting of nickel-chrome alloy.

28. A tubular furnace, means for peripherally supporting and rotating it to advance a stream of articles or materials therethrough, and means for projecting a flame jet in the opposite direction; said furnace including an outer tubular shell of rolled steel capable of supporting the entire load of the furnace; spaced-apart, inwardly-extending annular bearings carried by said Il outer shell; a. single-piece inner shell of rolled plate or heavy sheet, heat-resisting steel, longitudinally slidable to permit it to lengthen when heated: said inner shell having a radial exit chute rigidly secured adjacent the exit end thereof, and said outer shell having rigidly secured thereto, a

tubular member ntted to the exterior of said chute, whereby the inner shell is anchored to the outer shell near the exit end thereof, to prevent endwise sliding of said inner shell except by lengthening when heated.

GEORGE F. BLASIIERv 

